Method for charging the starter battery of a vehicle

Abstract

A method for charging the starter battery of a motor vehicle at a voltage source includes charging the starter battery after a traction battery of the vehicle has been charged up to a defined value. The starter battery is charged if a charge state of the starter battery is established that is below a defined threshold value. If the charge state of the starter battery is of such a low level, the starter battery is charged until one or more defined termination conditions are fulfilled. The termination conditions may include the total charging period since the low charge state of the starter battery has been established exceeds a defined threshold value and/or the total time period charging the traction battery and the starter battery at the voltage source exceeds a defined threshold.

What is claimed is: 
     
       1. A method for a vehicle having a traction battery, a starter battery, and a control module, comprising, by the control module:
 determining that the vehicle is connected to an external power supply, and while connected to the external power supply; 
 activating current supply from the external power supply to the starter battery in response to the traction battery exceeding a first threshold and the starter battery being below a second threshold; and 
 deactivating current supply from the external power supply a predetermined time after the starter battery exceeds a third threshold. 
 
     
     
       2. The method of  claim 1  further comprising, by the control module:
 periodically reactivating the current supply from the external power supply and monitoring a charge state of the starter battery; and 
 supplying current from the external power supply to the starter battery if the starter battery charge state falls below the second threshold. 
 
     
     
       3. The method of  claim 2  wherein the second threshold is a maximum desired charge state. 
     
     
       4. The method of  claim 1  wherein the first threshold is less than a maximum desired traction battery charge state. 
     
     
       5. The method of  claim 1  further comprising, by the control module, stopping current supply from the external power supply to the starter battery in response to a starter battery charging period exceeding a first time period. 
     
     
       6. The method of  claim 5  further comprising, by the control module, stopping current supply from the external power supply to the starter battery in response to a traction battery charging period exceeding a second time period.